This method receives $text, assumed to be encoded in {Site}{CharSet}, and
converts it to a internal representation.

Currently this representation will be a UTF-8 string, but this may change in
the future. This way, you can't assume any property on the returned value, and
should only use the returned value of this function as input to toSiteCharSet.
If you change the returnd value, either by removing, updating or appending
characters, be sure to touch only ASCII characters (i.e., characters that have
ord() less than 128).

This method receives a string, assumed to be encoded in TWiki's internal string
representation (as generated by the fromSiteCharSet method, and converts it
into {Site}{CharSet}.

When converting into {Site}{CharSet}, characters that are not present at that
charset are represented as HTML numerical character entities (NCR's), in the
format &#NNNN;, where NNNN is the character's Unicode
codepoint.